Plastered wall vs dot n dab plasterboard for bathroom?

pacman8

Hi,

In the process of renovating my bathroom and I've stripped it back to brick and concrete blocks. Expectedly, the wall is uneven. I'm new so unable to post a link to a pic.

I was initially going to get the walls plastered in preparation for tiling but read that a plastered wall can only handle around 20kg/sq meter of weight? The tiles I have are 600x300 and around 22kg/sq meter so not exactly the lightest.

An alternative solution recommended by a couple bathroom fitters is dotting and dabbing. Is this a good solution? If I did go down the dot and dab plasterboard route, I'd probably go for the green moisture resistant plasterboard tanking the boards in the wet area or possibly using something like Marmox, particularly for my external wall given I hear it has decent thermal properties... Does this sound like a solid plan or am I way off the mark and missing something here?

Thanks!

micky2phones

Hi, cannot answer you but many years i helped strip a bathroom down to the brickwork due to damp, behind the plasterboard was black growth.
Which if the walls had been plastered and not plasterboard it would not have happen so i was told.
But the main problem was the damp coming from the floor had no damp proofing

jk0

Neither!


I would batten the walls out with 22x47 treated vertical battens at 300mm spacing, and fix aquapanel. Put jointing tape over the joins and mud with water resistant tile adhesive.


Where there are no tiles, you can use plasterboard.

antilles

We refitted one of our bathrooms in the summer and had the same issue - we had to strip back the room all the way to the brickwork as the existing plasterboard under the tiles was wet and damaged due to leaks around the bath.

We used dot and dab as our research showed the same thing - it would hold more weight than a plastered wall.

We also used 600x300 tiles (large format porcelain tiles) which were extremely heavy. Have had no issues using dot and dab and it was fairly easy to level the walls using this method.

In terms of damp, I would think that it doesn't matter if the wall is plastered or plasterboard, water from a leak will penetrate it anyway (although it would probably penetrate a plastered wall much more slowly). The most important thing is to make sure there are no leaks and everything is waterproofed in the first place.

We tanked all the areas that would get wet before we tiled over the plasterboard. I would do this rather than wasting money on moisture resistant plasterboard, as by definition the boards are only 'moisture resistant' rather than waterproof, whereas the tanking is waterproof (it puts a rubber-like coat on the plasterboard). I guess they would provide an additional level of protection but I would guess that if the tanking was penetrated or water got into a non-tanked area, the boards would still rot anyway.

Also, be careful that you buy the correct tile adhesive, the one we initially bought was no good for the heavy porcelain tiles so we bought a rapid set one specifically for porcelain. And good luck cutting them.

As someone has also suggested, Aquapanel is a great alternative to tiling, the neighbours did this and it looks great - but we wanted tiles in the end.

Grenage

As you're replacing the tiling substrate anyway, I'd use the aforementioned Aquaboard.

pacman8

Thanks all. Lots of food for thought. I've read that aquaboard is water resistant, not water proof so although overkill, i'd probably end up tanking that in wet areas, just in case.

Any thoughts on the thermal element for the external wall?

**EDIT** - are aquaboard and aquapanel the same thing?

jk0

Aquapanel is not water 'proof'. It does not need to be if it's on battens. These allow a little air flow behind it and so it can dry out if there are any leaks. There really shouldn't be though, if you use water resistant tile adhesive and epoxy grout like I do.


Aquapanel is sold by Wickes: https://www.wickes.co.uk/Knauf-New-Aquapanel-Board---12-5mm-x-900mm-x-1-2m/p/207027

Grenage

Tile grout and adhesive is water resistant rather than water-proof, but in practice the water isn't going to get through unless there is an opening.


If the external wall is single-skin and cold, then I'd probably use Celotex or other rigid insulation - assuming you can afford the loss of space.

keithu

I've just dot-and-dabbed Orbry board (https://www.orbry.com/wet-rooms/orbry-boards/) to a bare brick bathroom wall. They recommend additional mechanical fixing with Spanker Dowels and are rated to hold 60kg per square metre.

andyhop

Strip the lot off including plaster, dot and dab standard square edge plasterboard as per spec. This will leave a flat and stable wall

Tank anything that will be near any water spray , for a bath or shower 3 coats of a paint on kit will suffice, for. Wetrooms use a sheet membrane